Difference between revisions of "Category:SQL"

Latest revision as of 09:25, 1 July 2017

tags:

[[Category:Computer Technology]]
[[Category:Programming]]
[[Category:SQL]]

Structured Query Language

SQL is a language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). SQL allows accessing many records with one single command, and eliminates the need to specify how to reach a record. SQL became a standard of the American National Standards Institute (ANSI) in 1986.

Originally called SEQUEL (Structured English Query Language), it was first developed by Donald D. Chamberlin and Raymond F. Boyce in the early 1970s for IBM. The acronym SEQUEL was later changed to SQL because "SEQUEL" was a trademark of the UK-based Hawker Siddeley aircraft company.

The SQL language is subdivided into several language elements, including:

• Clauses, which are constituent components of statements and queries. (In some cases, these are optional.)
• Expressions, which can produce either scalar values, or tables consisting of columns and rows of data
• Predicates, which specify conditions that can be evaluated to SQL three-valued logic (3VL) (true/false/unknown) or Boolean truth values and are used to limit the effects of statements and queries, or to change program flow.
• Queries, which retrieve the data based on specific criteria. This is an important element of SQL.
• Statements, which may have a persistent effect on schemata and data, or may control transactions, program flow, connections, sessions, or diagnostics. SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar.
• Insignificant whitespace is generally ignored in SQL statements and queries, making it easier to format SQL code for readability.